Metal mold device for blow molding

ABSTRACT

Fluid flow grooves ( 11 ) with a flat cross section being formed between the back surface of a metal mold ( 2 ) for blow molding and a back-up member ( 4 ) which adheres tightly to this back surface. A plurality of these fluid flow grooves ( 11 ) are provided, and these fluid flow grooves are disposed densely in parallel with partition walls ( 21 ) interposed between the grooves. Fluid inlets ( 12 ) and outlets ( 13 ) are formed in the respective fluid flow grooves ( 11 ). A heating fluid or cooling fluid enters the respective fluid flow grooves ( 11 ) via the inlets ( 12 ) from a fluid supply manifold ( 14 ). The fluid flows out of the outlets ( 13 ), enters a fluid discharge manifold ( 15 ), and is discharged to the outside. Rapid heating and rapid cooling of the metal mold ( 2 ) are performed, no irregularity occurs in temperature, and the cycle time can be shortened, so that a metal mold device for blow molding in which the energy consumption is small can be obtained.

TECHNICAL FIELD

The present invention relates to a metal mold device which is for blowmolding and is equipped with heating and/or cooling means.

BACKGROUND ART

In cases where high transfer properties and high-speed molding arerequired in blow molding, heating and cooling means are installed in themetal mold. More specifically, the metal mold is heated by the heatingmeans before the parison is supplied, and the outer surfaces of theparison in a softened state are caused to contact the inside surfaces ofthe heated mold so that high transfer properties are obtained.Furthermore, following this contact, the metal mold is forcibly cooledby the cooling means, so that the blow-molded body can be quicklyhardened and removed, thus shortening the cycle time. If high-speedheating and high-speed cooling of the metal mold are possible, then thecycle time can be shortened.

The following means are known as the above-described heating and coolingmeans:

(1) Means in which heating and cooling of the metal mold areaccomplished by laying pipes along the back surfaces of the metal mold,and alternately circulating a heating fluid (e.g., high-temperaturewater or high-temperature steam) and a cooling fluid (e.g., coolingwater) through these pipes. In this case, it is difficult to lay pipesso that these pipes adhere tightly to the back surfaces of the metalmold along the entire length of the pipes; furthermore, since the pipesare round, the contact area with the metal mold is also small.Accordingly, the heat exchange efficiency is poor, and the heating andcooling rates cannot increase.

(2) Means in which pipes (consisting of a metal whose melting point ishigher than that of the metal mold) are disposed inside the casting moldwhen the metal mold is cast, so that pipes are cast inside the walls ofthe metal mold. In this case, gaps are formed between the cast pipes andthe metal mold during use. Furthermore, since the pipes are round, thecontact area with the metal mold is small in relation to thecross-sectional area of the pipes. As a result, the heat exchangeefficiency is poor; and in addition, since the thickness of the metalmold must be increased, the thermal capacity of the metal moldincreases, and the heating and cooling rates do not increase.

(3) Means in which drill holes are formed vertically and horizontallyinside the walls of the metal mold from the back surfaces of the metalmold, and are caused to communicate with each other, and a heating orcooling fluid is circulated through these holes. In this case, theadvantage of direct contact of the heating or cooling fluid with themetal mold is obtained. However, since the drill holes are round so thatthe contact area between the metal mold and the fluid is small inrelation to the cross-sectional area, the heat exchange efficiency ispoor. In addition, since the thickness of the metal mold must be large,the thermal capacity of the metal mold is large. Moreover, since thedrill holes can only be formed in a rectilinear configuration, it may beimpossible (depending on the shape of the metal mold) to form therequired number of holes, so that the heating and cooling rates cannotincrease.

(4) Means in which spaces are formed on the back surface sides of themetal mold, and the metal mold is heated or cooled by circulating aheating or cooling fluid through these spaces (see Japanese PatentApplication Laid-Open (Kokai) No. 9-164583). In this case, since theheating or cooling fluid is circulated through large spaces, a largequantity of fluid is required, and the thermal capacity of the metalmold as a whole surrounding the spaces is also large; as a result, alarge quantity of energy is consumed. In addition, since the fluidloiters (has a slow flow velocity) inside the spaces, the heat exchangeefficiency is poor, and the heating and cooling rates cannot increase.

(5) Means in which thin plate bodies that form a cavity are disposed onthe joining surfaces of the metal mold main body, and a narrow gap isformed between the metal mold main body and the thin plate bodies, andcooling of the metal mold is accomplished by causing a cooling medium toflow through this gap (see Japanese Patent Application Laid-Open(Laid-Open (Kokai)) No. 10-235722). In this case, though rapid coolingof the thin plate bodies that form the cavity is possible, non-uniformflow of the cooling medium occurs inside the gap, and the cooling ratevaries according to the position, thus tending to cause irregularitiesin the metal mold temperature.

DISCLOSURE OF INVENTION

The present invention is made in light of the above-described problemsin conventional heating and cooling means; and the object of the presentinvention is to provide a metal mold device for blow molding in whichsufficiently rapid heating and sufficiently rapid cooling of the metalmold are accomplished, no irregularity occurs in the metal moldtemperature, and the amount of energy that is consumed can be small.

In the metal mold device for blow molding of the present invention,fluid flow grooves with a flat cross section are formed between the backsurface of a metal mold which is used for blow molding and a back-upmember which is disposed so as to adhere tightly to the back surface,the fluid flow grooves are provided in a plurality of numbers and aredisposed so that the grooves are densely concentrated with partitionwalls interposed, and fluid inlet openings and outlet openings areformed in each of the fluid flow grooves; and heating or cooling of themetal mold is accomplished by causing a heating fluid or cooling fluidto flow through each of the fluid flow grooves. Though this goes withoutsaying, the above-described flat fluid flow grooves are flattened alongthe back surface of the metal mold.

The above-described inlets and outlets can be formed in the back-upmember. In addition, the inlets and outlets of the respective fluid flowgrooves can be caused to communicate with the piping of a fluid supplyor discharge manifold, so that the fluid is supplied or discharged viathese manifolds. It is preferable that the manifolds be disposed insidethe metal mold structural body on the back surface side of the metalmold (these manifolds can be formed in a back-up member disposed insidethe metal mold structural body), and that the manifolds be caused tocommunicate with an external fluid source. It is desirable that theback-up member be formed from a material that has a lower thermalconductivity than the metal mold.

In the above-described metal mold device for blow molding, eitherheating or cooling alone of the metal mold can be performed, or a cycleof heating and cooling can be repeated. High transfer properties can beobtained by supplying a heating fluid (e.g., high-temperature water orhigh-temperature steam) prior to the supply of the parison so that themetal mold is heated and by causing the outside surfaces of the parisonin a softened state to contact the heated inside surfaces of the metalmold. Meanwhile, if the heated metal mold is cooled by supplying acooling fluid (e.g., cooling water) after the parison has contacted theinside surfaces of the metal mold, the blow-molded article can bequickly cooled and hardened, so that the molded article can be quicklyremoved from the metal mold. Accordingly, the cycle time can beshortened so that high-speed molding is accomplished. Furthermore, byway of alternately performing heating and cooling, high transferproperties and high-speed molding are both achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a horizontal sectional view (a sectional view along the lineI—I in FIG. 3) which shows in schematic terms the metal mold device forblow molding according to the present invention.

FIG. 2 is a horizontal sectional view (along the line II—II in FIG. 3)of the metal mold device in a separate location.

FIG. 3 is a side view of the back-up member.

FIG. 4 is a sectional view that illustrates another method of formingthe fluid flow grooves.

FIG. 5 is a perspective view (sectioned along the line III—III in FIG.7) which illustrates, in more concrete terms, the metal mold device forblow molding according to the present invention.

FIG. 6 is a sectional view (along the line III—III in FIG. 7) thereof.

FIG. 7 is a bottom view that shows the structure of the metal mold andback-up member with the back plate removed.

BEST MODE FOR CARRYING OUT THE INVENTION

The metal mold device for blow molding according to the presentinvention will be described below with reference to the schematicdiagrams shown in FIGS. 1 through 4.

The metal mold device 1 for blow molding shown in FIG. 1 (only one sideis shown) comprises a metal mold 2 which has a cavity portion 3, aback-up member 4 which is disposed inside the metal mold structural bodyand on the back surface side of the metal mold 2, a back plate 5 whichsupports the back of the metal mold 2, and reinforcing members 6 whichsupport the back plate 5 and are connected to an opening-and-closingmechanism, etc. The above-described cavity portion 3 is in the areasurrounded by pinch-off portions 7 and 8, and contact portions 9 and 10are formed on the left and right ends of the metal mold 2. The pinch-offportions 7 and 8 are the areas where cutting of the parison isperformed. The contact portions 9 and 10 contact the contact portions ofa metal mold (not shown in the drawings; a cavity space is formed by onepair of metal molds) which is disposed so as to face the above-describedmetal mold 2, and such contact portions 9 and 10 demarcate the closestpositions of the two metal molds. The contact portions 9 and 10 also actto prevent damage that might be caused by the pinch-off portions 7 and 8that contact the pinch-off portions of the facing metal mold. In theabove metal mold device 1 for blow molding, the parison is disposedperpendicular to the drawing sheet surface.

The surface of the back-up member 4 adheres tightly to the back surfaceof the metal mold 2 and is disposed completely inside the structuralbody of the metal mold. A plurality of flattened recessed grooves 11 areformed substantially parallel to each other in the surface of theback-up member 4, over substantially the entire left-right length of theback-up member 4 as shown in FIG. 3, and these recessed grooves 11 aredensely concentrated with partition walls 21 which have a narrow widthand are interposed between the grooves. The respective recessed grooves11 are surrounded by the partition walls 21 and dikes 22 which areformed on the periphery of the surface of the back-up member 4; and inthe left and right end portions of each recessed groove 11, an inlet 12is formed at one end and an outlet 13 is fanned at the other end. Therespective inlets 12 communicate with a fluid supply manifold 14 whichis formed inside the back-up member 4, and the respective outlets 13communicate with a fluid discharge manifold 15 which is similarly formedinside the back-up member 4. The manifolds 14 and 15 respectivelyinclude piping portions 14 a and 15 a and common collecting chambers 14b and 15 b. The piping portions 14 a and 15 a are respectively connectedto the respective inlets 12 and outlets 13, and the common collectingchambers 14 b and 15 b respectively communicate with the piping portions14 a and 15 a. The collecting chambers 14 b and 15 b are closed off bythe bank plate 5 and communicate with the outside via conducting pipes16 and 17.

A vent manifold 18 that communicates with the vent holes (describedlater) of the metal mold 2 is formed in the back-up member 4. The ventmanifold 18 is comprised of piping portions 18 a and a common collectingchamber 18 b with which these piping portions 18 a communicate. Thiscollecting chamber 18 b is closed off by the back plate 5 andcommunicates with the outside via a conducting pipe not shown in thedrawings.

Small vent holes 19 are formed in the cavity portion 3 of the metal mold2 and led to the inside surface. The vent holes 19 communicate with thepiping portions 18 a of the vent manifold 18 via piping portions 20inside the metal mold 2. As seen from FIG. 3, the vent holes 19 andpiping portions 20 of the metal mold 2 and the piping portions 18 a ofthe vent manifold 18 are disposed between the recessed grooves 11 of theback-up member 4.

From the standpoint of rapid heating and rapid cooling, and from thestandpoint of energy consumption, it is preferable that the thickness ofthe metal mold 2 be thin. However, if the metal mold is too thin,irregularity in heating or cooling tends to occur at the surface of themetal mold 2; and further when pressing force of blow molding isapplied, deformation occurs, making it difficult to maintain the desiredcavity shape. The thickness of the metal mold 2 is set withconsideration given to these points. If the material of the metal mold 2is an aluminum alloy, the thickness may be set in the range of, forexample, 4 to 15 mm, with the shape and size, etc. of the cavity portiontaken into account. By way of setting the thickness of the metal mold 2as small as this, the thermal capacity is reduced, rapid heating andrapid cooling are possible, and the energy consumption is reduced.

The back surface of the metal mold 2 and the surface of the back-upmember 4 adhere tightly to each other so that the cross sections of therecessed grooves 11 are closed, thus forming flattened fluid flowgrooves. The depth of these fluid flow grooves (or the recessed grooves11) is appropriately set with consideration given to the quantity ofheat that is exchanged by heat exchange. However, if the fluid is causedto pass through at a high speed, the heat exchange efficiency is high,the amount of fluid that flows through is relatively small, and theamount of energy that is consumed is small; accordingly, theabove-described depth is selected from a range of, for example, 0.5 to 7mm. If the depth of the fluid flow grooves is greater than such values,then the fluid flows only in the center of the depth, and the heatexchange efficiency does increase. The depth value is preferablyselected from a range of 0.5 to 3 mm. The width of the grooves is to beset appropriately, and the width is selected, for instance, from a rangeof 10 to 50 mm. If the width is outside this range, irregularity occursin the cooling rate or heating rate in the direction of width. The widthvalue is preferably selected from a range of 10 to 40 mm.

In order to prevent the leakage of fluid from the fluid flow grooves(recessed grooves 11), gaskets can be interposed, if necessary, aroundthe peripheries of the recessed grooves 11 between the back surface ofthe metal mold 2 and the surface of the back-up member 4. Gaskets can beinterposed also around the peripheries of the collecting chambers 14 band 15 b between the back-up member 4 and the back plate 5 in order toprevent the leakage of fluid from these collecting chambers 14 b and 15b of the manifolds 14 and 15.

In the above-described metal mold device 1, the heating fluid or coolingfluid enters the collecting chamber 14 b of the fluid supply manifold 14via the conducting pipe 16 from an external supply device, and suchfluid is distributed into the respective piping portions 14 a. From therespective piping portions 14 a, the fluid enters the respective fluidflow grooves (recessed grooves 11) via the respective inlets 12 andflows at a high speed along the back surface of the metal mold 2. Duringthis period, rapid heat exchange is performed between the fluid and themetal mold 2. The fluid reaching the end portions of the respectivefluid flow grooves (recessed grooves 11) flows out into the respectivepiping portions 15 a of the fluid discharge manifold 15 via therespective outlets 13 and enters the collecting chamber 15 b, and thenthe fluid is discharged to the outside via the conducting pipe 17. Thefluid supply manifold 14 has also the function of uniformly distributingthe fluid among the respective fluid flow grooves (recessed grooves 11);and in addition to collecting the fluid discharged from the respectivefluid flow grooves (recessed grooves 11), the fluid discharge manifold15 has also the function of releasing the pressure of the steam formedby vaporization of the fluid that occurs when the fluid contacts theheated back surface of the metal mold during cooling.

In the above-described metal mold device 1, the collecting chamber ofthe vent manifold 18 can be communicated with a vacuum suction device,so that a vacuum can be applied. In this case, even if there fluidleakage occurs from the fluid flow grooves (recessed grooves 11), thefluid can be discharged via the piping portions 18 a.

Alternatively, the leakage of air, etc. can be prevented by interposingO-rings, etc., around the peripheries of the contact portions betweenthe piping portions 20 of the metal mold 2 and the piping potions 18 aof the vent manifold 18.

In the above-described example, the piping portions 20 and pipingportions 18 a are disposed between the recessed grooves 11 (see FIG. 3);however, these piping portions can be provided inside the recessedgrooves 11. In this case, it is necessary to close off the pipingportions 20 and piping portions 18 a from the fluid flow grooves(recessed grooves 11) so that the heating fluid or cooling fluid doesnot enter the piping portions 20 and piping portions 18 a.

In the above-described example, the back-up member is disposed insidethe metal mold structural body, the fluid supply manifold and fluiddischarge manifold are formed in the back-up member itself, and the ventmanifold, etc. are also provided in the back-up member. However, it ispossible to limit the role of the back-up member to the formation offluid flow grooves between the back-up member and the back surface ofthe metal mold as shown in FIG. 4. More specifically, in FIG. 4( a),flattened recessed grooves 33 are formed in the back surface of themetal mold 32 in a configuration similar to that of the above-describedrecessed grooves 11, and fluid flow grooves (or the recessed grooves 33)are formed by covering these recessed grooves 33 with a plate-formback-up member 34. In FIG. 4( b), a plate form back-up member 44 whichhas recessed grooves 43 of a configuration similar to that of theabove-described recessed grooves 11 is disposed on the back surface of ametal mold 42 similar to the metal mold 2, so that fluid flow grooves(or the recessed grooves 43) are formed thereby. In the above examples,it is necessary to separately install a fluid supply manifold thatsupplies the fluid to the fluid flow grooves and a fluid dischargemanifold that discharges the fluid from the fluid flow grooves, so thatthese manifolds communicate with the fluid flow grooves.

Next, the metal mold device for blow molding according to the presentinvention will be described more concretely with reference to FIGS. 5through 7.

The metal mold device 51 for blow molding shown in FIGS. 5 through 7(only one side of the device is shown) is used to manufacture a rearspoiler for automobiles, and it comprises a metal mold 52 which has acavity portion 53, back-up members 54 through 58 which are disposedinside the metal mold structural body and on the back surface side ofthe metal mold, and a back plate 59 which supports the back of the metalmold 52. The cavity portion 53 is in the range surrounded by thepinch-off portions 60, and contact portions 61 and 62 are formed on theleft and right ends of the metal mold 52. The metal mold device 51 forblow molding is disposed so that the direction of length of the cavityportion 53 is vertically oriented (the vertical direction is shown inFIG. 7), and the parison is disposed in the direction of length of thecavity portion 53.

The cavity portion 53 of the metal mold 52 is formed with a smallthickness, and numerous flattened recessed grooves 64 are formed in theback surface. The grooves are provided so as to be densely concentratedin parallel with partition walls 65, which have a small thickness,interposed between the grooves. The respective recessed grooves 64 aresurrounded by the partition walls 65 and dikes 66 that are around theperiphery of the back surface of the cavity portion 53.

The back-up member 54 is disposed in the central portion inside thestructural body of the metal mold 52 (or in the hollow portion on theback side of the cavity portion 53), and the surface of this back-upmember 54 is caused to adhere tightly to the partition walls 65 anddikes 66 on the back surface of the cavity portion 53. As a result, thecross sections of the recessed grooves 64 are closed off, and flattenedfluid flow grooves are formed. Furthermore, inlet/outlets 67 and 68 (asshown in FIG. 7, and the inlet/outlets in the upper half are designatedby the reference numeral 67, and the inlet/outlets in the lower half aredesignated by the reference numeral 68) are formed in the surface of theback-up member 54 in locations that correspond to one end portion ofeach recessed groove 64, and inlet/outlets 69 and 70 (as shown in FIG.7; and the inlet/outlets in the upper half part are designated by thereference number 69, and the inlet/outlets in the lower half part aredesignated by the reference number 70) are formed in locations thatcorrespond to the other end portion of each recessed groove 64. Therespective inlet/outlets 67 through 70 communicate with manifolds 71through 74 formed inside the back-up member 54. The manifolds 71 through74 are respectively comprised of piping portions 71 a through 74 a,which connect with the respective inlet/outlet 67 through 70, and commoncollecting chambers 71 b through 74 b, which are formed in the backsurface side of the back-up member 54. The collecting chambers 71 bthrough 74 b are closed off by a back plate 59; and in this back plate59, communicating holes 75 through 78 (indicated by dotted imaginarylines in FIG. 7) that cause the collecting chambers 71 b through 74 b tocommunicate with the outside are formed.

In cases where water is used as a cooling medium and steam is used as aheating medium, water is supplied to the collecting chambers 72 b and 73b of the manifolds 72 and 73 via the communicating holes 76 and 77during cooling. This water passes through the piping portions 72 a and73 a and the inlet/outlets 68 and 69 and enters the fluid flow grooves(recessed grooves 64). The water flows along these fluid flow groovesand enters the collecting chambers 74 b and 71 b via the inlet/outlets70 and 67 and the piping portions 74 a and 71 a of the manifolds 74 and71. The water is then discharged to the outside via the communicatingholes 78 and 75. During heating, steam flows through in the directionopposite from the direction of flow of the water during coolingdescribed above.

Side portions 80 and 81 of the cavity portion 53 of the metal mold 52are formed so that both of these side portions are thin along thedirection of length, and the back surfaces have a semicircular shape incross section. The back-up members 55 through 58 are disposed inside thestructural body of the metal mold 52 (in the hollow portions on the backsides of both side portions 80 and 81), and the front surfaces aredisposed at a specified distance from the back surfaces of both sideportions 80 and 81. As a result, flattened circular-arc-form coolingwater flow grooves 82 whose cross sections are closed off are formed.Furthermore, inlets 83 through 86 and outlets 87 through 90 are formedon the surfaces of the back-up members 55 through 58 in locations thatcorrespond to both side portions of the respective cooling water flowgrooves 82. The respective inlets 83 through 86 and outlets 87 through90 communicate with cooling water inlet passages 91 through 94 andcooling water outlet passages 95 through 98 similarly formed inside theback-up members 55 through 58 and further with inlet holes and outletholes (the outlet holes 99 are shown in FIG. 5) formed in the back plate59.

The reference numeral 100 indicates hollow spaces formed in order toreduce the weight, 101 indicates an annular gasket that prevents theleakage of fluid, 102 indicates a temperature detection sensor, and 103indicates vent pipes that communicate with vent holes formed in thecavity portion 53 of the metal mold 52.

In the present invention, since flattened fluid flow grooves are formedby the metal mold for blow molding and back-up members that adheretightly to the back surface of this mold, the heating fluid or coolingfluid directly contacts the back surface of the metal mold; furthermore,the fluid flow grooves are densely concentrated on the back surface ofthe metal mold. Accordingly, an increased contact area between the metalmold and the fluid is secured, and a superior heat exchange efficiencyis obtained. Thus, rapid heating and rapid cooling of the metal mold arepossible, the cycle time can be shortened, and the energy consumptioncan also be reduced.

Furthermore, since a plurality of fluid flow grooves are disposed withpartition walls in between, and since fluid inlets and outlets areformed in the respective fluid flow grooves, local stagnation of thefluid in the fluid flow grooves tends not to occur, and heating orcooling with no irregularity overall can be accomplished.

1. A metal mold device for blow molding characterized in that: fluidflow grooves with a flat cross section are formed between a back surfaceof a metal mold which is used for blow molding and a back-up memberwhich is disposed so as to adhere tightly to said back surface, saidflat cross section being flattened along said back surface of said metalmold, said fluid flow grooves are provided in a plurality of numbers andare disposed so that said grooves are densely concentrated witHpartition walls, which have a narrow width, interposed, and fluid inletopenings and outlet openings are formed in each of said fluid flowgrooves, said fluid inlet openings being at one end thereof and saidoutlet openings being at another end thereof; wherein heating or coolingof said metal mold is accomplished by causing a heating fluid or coolingfluid to flow through each of said fluid flow grooves.
 2. The metal molddevice for blow molding according to claim 1 characterized in that saidflat cross section of each of said fluid flow grooves has a width of10–50 mm and a depth of 0.5–7 mm on said back surface of said metalmold.
 3. The metal mold device for blow molding according to claim 2characterized in that said fluid flow grooves have a depth of 0.5–3 mm.4. The metal mold device for blow molding according to claim 1, 2 or 3characterized in that said inlets and outlets are formed in said back-upmember.
 5. The metal mold device for blow molding according to claim 1,2 or 3 characterized in that said inlets and outlets of said respectivefluid flow grooves respectively communicate with a piping of a supply ordischarge manifold.
 6. The metal mold device for blow molding accordingto claim 4 characterized in that said inlet and outlet of each one ofsaid fluid flow grooves are respectively communicated with a piping of afluid supply manifold and a piping of a fluid discharge manifold.